Film handling means for a laser recorder

ABSTRACT

A laser recorder applicable to computer output microfilm recording apparatus comprises: a housing, a film feed unit having a film cassette loaded with a rolled heat development film; a film take-up unit for taking up the heat development film on a reel or on a tray, including a film storing mechanism for storing cut films sequentially; a main driving unit for driving the heat development film for advancing at a fixed speed for auxiliary scanning for recording image information on the heat development film, including a slackened film relief mechanism for eliminating slackened film around the main driving unit and a stepping motor driving current control circuit for driving the main driving unit at a low and fixed speed; loop detectors for preventing film feed force and film delivery force from working on the main driving unit, an image information recording unit for main scanning, having a laser optical system for scanning the heat development film across the width thereof to record image information recorded on the heat development film thereon; and a heat-development unit for heat-developing the image information recorded on the heat development film, including a delivery driving roller unit and a guide roller unit driven at different speeds respectively for eliminating slackened film around the heat-development unit as well as controlling the heat-development time, a temperature controller for controlling heat-development unit temperature, and a swing roller for separating the film from the heat-development unit when heat-development is not required.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a laser recorder suitable for use, forexample, as a computer output microfilm producing apparatus (hereinafterabbreviated to "COM apparatus") which records image information on a drysilver halide photographic film by using a laser beam emitted from alaser, and then develops the image information by a heat developmentprocess.

2. Discussion of the Prior Art

Improvement of the performance and enhancement of the functions ofreproducing apparatus for reproducing the output of informationprocessing equipment including computers have become a significantsubject of research and development with the progressive development ofhigh-performance information processing equipment. Among thosereproducing apparatus, reproducing apparatus employing a laser lightsource, such as laser printers and the like, are the most prospectivereproducing apparatus. For example, U.S. Pat. No. 4,257,053 discloses abasic method and construction of a plotter using a laser as a lightsource. Japanese Patent Application Laid-Open NO. SHO 59-116748discloses a heat-developing device wherein a laser beam is radiated to aheat development film. Japanese Patent Application Laid-Open No. SHO57-193170 discloses a laser recorder where the auxiliary scanning isoperated by a stepping motor. However, the conventional reproducingapparatus have not been satisfactory in size and performance. With COMapparatus also, the furtherance of reduction in size, particularly inthickness, simplification of operation and improvement of theperformance have become necessary with the development of highperformance information processing equipment.

SUMMARY OF THE INVENTION

Therefore, it is an object of the present invention to provide a laserrecorder capable of forming a more accurate image on a film by radiatinga laser beam on the film, by driving the heat development film in thedirection of auxiliary scanning at a low speed and improving theaccuracy in driving the film.

It is a further object of the present invention to provide a controlmechanism for maintaining fixed ranges of the size of loops before andafter the main driving roller, which drives the film for running at afixed speed, with respect to the direction of running of the film, andmore particularly, to stabilize the speed of the film driving on themain driving roller by maintaining the above mentioned loop by changingthe film driving speed in a range that does not affect the quality ofimages.

It is a further object of the present invention to bring the film intoclose contact with a driving roller, by absorbing slack of the filmwhich occurs upon the initial setting of the film on the driving roller,on the main driving roller portion having a plurality of pressurerollers in the film conveying unit.

It is an object of the present invention to provide a laser recorder inwhich the film, being constantly brought into contact with the heatdevelopment unit, is separated from the heat development unit while itis unnecessary to be heat-developed.

It is a further object of the present invention to obtain the rightorder of pieces of film which are cut into predetermined lengths anddischarged to be collected, by making a layer between the edge portionof a piece of film and the edge portion of the next piece of film,enabling the pieces of film to be in right order in a followingconveying process also, in the conveying unit.

It is a further object of the present invention to prevent unevenness ofimage density on the film by giving a predetermined degree of tension tothe film to bring the film into close contact with the heat developmentunit when developing the film at the heat development unit.

It is a further object of the present invention to keep the heat rollerat a fixed temperature by detecting the surface temperature of the heatroller storing the obtained data, and controlling the control current ofthe heater in the heat development unit on the basis of the storedtemperature data and the present temperature data.

It is a further object of the present invention to give a main drivingroller a smooth rotation by employing a stepping motor as a drivingmeans of the main driving roller, and finely changing the current byfurther dividing each step angle of each step pulse instead of anelectric pulse as a driving signal.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and features of the invention will become apparent tothose skilled in the art as the disclosure is made in the followingdescription of preferred embodiments of the invention, as illustrated inthe accompanying sheet of drawings, in which:

FIG. 1 is a perspective schematic illustration showing the configurationof a laser recorder, in a preferred embodiment, according to the presentinvention;

FIG. 2 is a schematic front view showing the configuration of a laserrecorder, in a preferred embodiment, according to the present invention;

FIG. 3 is a chart showing the driving current waveform of steppingmotor, controlled by the driving current control circuit, according tothe present invention;

FIG. 4 is a chart showing the driving current waveform of a conventionaltype stepping motor;

FIG. 5 is a circuit diagram showing the stepping motor driving circuitof the preferred embodiment according to the present invention;

FIG. 6 is a schematic enlarged illustration of the major sections of theslackened film release mechanism for keeping film in close contact withthe main driving roller in the preferred embodiment according to thepresent invention;

FIGS. 7 and 8 are schematic front views showing the major sections ofthe mechanism for pressing and separating the film to and from the heatroller according to the present invention;

FIGS. 9 and 10 are schematic front views showing the major sections ofthe first alternative for the mechanism for pressing and separating thefilm to and from the heat roller according to the present invention;

FIGS. 11 and 12 are schematic front views showing the major sections ofthe second alternative for the mechanism for pressing and separating thefilm to and from the heat roller according to the present invention;

FIG. 13 is a schematic enlarged illustration showing the thirdalternative for the mechanism for pressing to and from the heat rolleras well as the major sections of heat roller surface temperaturecontroller according to the present invention;

FIG. 14 is a circuit diagram showing the heat roller surface temperaturecontroller circuit;

FIG. 15 is a chart for explaining the heat roller surface temperaturecontrol according to the present invention;

FIG. 16 is a chart for explaining the heat roller surface temperaturecontrol by pulse width modulation control in the heat roller surfacetemperature controller according to the present invention;

FIG. 17 is a schematic enlarged illustration showing the major sectionsof film storing mechanism according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 and 2, a laser recorder in a preferred embodiment,according to the present invention, is explained in general.

The laser recorder in the preferred embodiment comprises a housing 1, afilm feed unit 2, a heat-developed film take-up unit 3, a main drivingunit 4, an image information recording unit 5, a heat-development unit6, and a controller. The film feed unit 2, the heat-developed filmtake-up unit 3, the main driving unit 4, the image information recordingunit 5, the heat-development unit 6, and the controller are disposed inthe housing 1 shut and enclosed from the environment so as to form adark room.

The film feed unit 2 comprises a cassette for a rolled heat-developmentfilm 100 which is disposed in the lower section of the housing 1. Forthe rolled heat-development film (hereinafter referred to as film), a 16mm dry silver halide film, such as a DAKOMATIC film registeredtrademark; produced by Eastman Kodak Co.) may be used.

The heat-developed film take-up unit 3 is disposed in the upper sectionof the housing 1 so that a vertically long film path is formed betweenthe film feed unit 2 and the heat-development film take-up unit 3. Theheat-development film take-up unit 3 comprises a film take-up reel 31,disposed in the upper section of the housing 1, and a tray 32 forstoring cut films, disposed at the outside of the housing 1. Filmadvancement direction can be switched either to the film take-up reel 31or to the tray 32 by a switching device, not shown, as desired.Therefore, depending on film applications, the heat-developed film istaken up by the film take-up reel 31 when a roll of film is required, oris stored in the tray 32 after being cut by a cutter 33 when cut filmsare required.

The main driving unit 4 is for driving the film 100 at a fixed speed,and is disposed between the film feed unit 2 and the heat-developed filmtake-up unit 3 on the film path 10 in the middle section of the housing1.

The controller is for controlling the film feed unit 2, theheat-developed film take-up unit 3, the main driving unit 4, the imageinformation recording unit 5, and the heat-development unit 6.

Forming Loops before and after the Main Driving Roller and LoopDetectors

Referring to FIGS. 1 and 2, a laser recorder, comprising loop detectors,according to the present invention, is explained.

The main driving unit 4 comprises a main driving roller 41, which isdriven by a stepping motor (not shown) at a low speed, and whose outercircumference is brought into contact with the film 100, and at leasttwo pressure rollers 42 and 43, which press the film 100 against theouter circumference of the main driving roller 41, a feed driving rollerunit 110, which feeds the film 100 to the main driving unit 4 whilemaintaining looped state of the film 100, and a delivery driving rollerunit 61, which delivers the film 100 to the later-describedheat-development film unit 6 while maintaining looped state of the film100. Thus, this construction does not allow the film 100 feed anddeliverly force to work on the main driving roller 41.

A first film loop detector 7 and a second loop detector 8 are disposedbetween the main driving roller 41 and the feed driving roller unit 110,and between the main driving unit 41 and the delivery driving rollerunit 61, respectively. Film guides 73 and 83 are provided between thefirst loop detector 7 and the main driving roller 41 and between themain driving roller 41 and the second loop detector 8, respectively. Thefeed driving roller unit 110 and the delivery driving roller unit 61 arecontrolled according to signals generated by the first and the secondfilm loop detectors 7 and 8, respectively.

The feed driving roller unit 110 comprises a smaller diameter drivingroller 111, interlocking with a motor which starts and stops the roller111 according to ON and OFF signals generated by the first loop detector7. The feed driving roller unit 110 also includes a larger diameterdriven roller 112, which is brought into contact with the driving roller111 through the film 100 and is driven by the driving roller 111. Thedelivery driving roller unit 61 comprises a smaller diameter drivingroller 611, interlocking with a motor which starts and stops the roller611 according to ON and OFF signals generated by the second loopdetector 8. The delivery during roller unit 61 also includes; a largerdiameter driven roller 612, which is brought into contact with thedriving roller 611 through the film 100 and is driven by the drivingroller 611. The first loop detector 7, disposed between the main drivingunit 4 and the feed driving roller unit 110, comprises two pairs of aninfrared ray emitting diode 71 and a photodiode 72 which are installedon a board 7a. The second loop detector 8, disposed between the maindriving unit 4 and the delivery driving roller unit 61, comprises twopairs of an infrared ray emitting diode 81 and a photodiode 82 which areinstalled on a board 8a. Thus, loop amounts of the film 100 between theinfrared ray emitting diode 71 and the photodiode 72, and between theinfrared ray emitting diode 81 and the photodiode 82, are detected bythe first and the second loop detectors 7 and 8. The detectors 7 and 8transmit the ON or OFF signal to the feed driving roller unit 110 andthe delivery driving roller unit 61 depending on loop amounts of thefilm 100. Thus, the feed driving roller unit 110 and the deliverydriving roller unit 61 can be activated or deactivated.

In the laser recorder as constructed above, the rolled heat-developmentfilm 100, loaded in the film feed unit 2, is drawn out of the film feedunit 2 and set along the film path 10 in advance in the housing 1 shutand enclosed from the environment so as to form a dark room.

When the laser recorder is actuated, the film feed unit 2, the feeddriving roller unit 110, the main driving unit 4, the delivery drivingroller unit 61, and advancement driving rollers 130 start working. Then,the film 100 is delivered to the main driving unit 4 by the feed drivingroller unit 110 while maintaining the looped state. The film 100 isadvanced by the main driving roller 41 driven by a stepping motor (notshown) while being pressed against the outer circumference of the maindriving roller 41 by two pressure rollers 42 and 43. When the film 100advances on the main driving roller 41, the laser beam generated by theimage information recording unit 5 is radiated onto the surface of thefilm 100 opposite to the surface contacting with the main driving roller41. The film 100, on which image information is recorded by the imageinformation recording unit 5, is delivered to the heat-development unit6 while maintaining the looped state between the main driving roller 41and the delivery driving roller unit 61. And then, the film 100 surfaceopposite to the surface onto which the image information recording unit5 radiates the laser beam, is brought into contact with theheat-developed film unit 6 where the film 100 is heat-developed. Afterheat-development, the film 100 is advanced via the image densitydetector 9 to the film take-up unit 3 by the advancement driving rollers130, and the film 100 is stored in the heat-developed film take-up unit3.

In this laser recorder operation, the film 100, drawn out of the filmfeed unit 2, advances while maintaining its looped states between themain driving roller 41, with which the film 100 is brought into contactand which revolves at a low speed, and the feed driving roller unit 110at the feed side, from which the film 100 approaches the main drivingroller 41, and between the main driving roller 41 and the deliverydriving roller unit 61 at the discharge side, for which the film 100leaves the main driving roller 41. Thus, no force for feeding anddelivering the film 100 works on the main driving roller 41 and on thefilm 100 which is at a position contacting with the main driving roller41.

Therefore, the revolving speed of main driving roller 41 issubstantially stabilized. And not only the advancement speed of the filmsurface, onto which the laser beam is radiated, is stabilized but also alowspeed and highly accurate film delivery condition is achieved,because the film 100 advances under the condition that the film surfaceopposite to the laser beam radiated surface is pressed against and isbrought into contact with the outer circumference of the main drivingroller 41 by the pressure rollers 42 and 43.

Accordingly, the laser beam radiation on the heat-development film inthe auxiliary scanning direction is performed highly accurately, andimage information is recorded favorably.

Further to the above described advantages, no force for feeding anddelivering the film 100 works on the main driving roller 41, and thestate can be always maintained, because the above described film 100loop amounts are detected by the first and the second loop detectors 7and 8, and the feed driving roller unit 110 and the delivery roller unit61 are controlled according to signals generated by the first and thesecond detectors 7 and 8.

For an alternative to the above second loop detector, the second loopdetector may be constructed so as to work as follows:

When the upper limit sensors of the second loop detector 8 detect thefilm 100, the film advancement speed of delivery driving roller unit 61is increased by an amount, which does not adversely affect imagequality, namely by approximately ±2% of the base speed of the motor fordriving the main driving roller 41. And when the lower limit sensors ofthe second loop detector 8 do not detect the film 100, the filmadvancement speed of delivery driving roller unit 61 is decreased by anamount, which does not adversely affect image quality, namely byapproximately ±2% of the base speed of the motor to restore the film 100loop amount falling between the upper and lower limits.

Similarly, the first loop detector 7 works to stop and start the feeddriving unit 110 as described above.

The alternative embodiment also provides the same advantages which havebeen described above i.e., a highly accurate laser scanning in theauxiliary direction as well as the mechanism which prevents film feedingand delivering forces from working on the main driving roller 41.

Although the film loop detectors have been described as applied to thelaser recorder, the film loop detectors according to the presentinvention are not limited thereto in its application. The film loopdetector is effectively applicable to an advancement means for acontinuous recording medium, etc. requiring an accurate film feed speedon the main driving roller.

Slackened Film Relief Mechanism

Referring to FIG. 6, the laser recorder comprising a slackened filmrelief mechanism for keeping the film 100 in close contact with the maindriving roller 41, according to the present invention, is explained.

The main driving roller 41 is driven by a motor (not shown), such as astepping motor. Pressure rollers 42 and 43 are pressed, respectively,against the main driving roller 41 at the opposite circumferential endsof a section in the circumference of the main driving roller 41 in whichthe film 100 is exposed to the laser beam to write image information onthe film 100. The main driving roller 41 is driven for rotation by thestepping motor so that the film 100 is advanced at a fixed speed.

In order to eliminate slack 340 of film 100 on the circumference of themain driving roller 41, the laser recorder is provided with a slackenedfilm relief mechanism for pressing the first pressure roller 42 againstthe main driving roller 41 and separating the first pressure roller 42from the main driving roller 41. The slackened film relief mechanismcomprises a swing arm 350 rotatably supporting the pressure roller 42 atone end thereof and having a finger 370 perpendicularly extending fromthe body thereof, a shaft 360 pivotally supporting the swing arm 350 atthe other end of the same, a bracket 380 attached to the free end of thefinger 370, and a solenoid 390 contacting the bracket 380.

In operation, upon the start of the motor to rotate the main drivingroller 41, the solenoid 390 is energized to push the bracket 380, andthereby the swing arm 350 is swung around the shaft 360 in a directionindicated by an arrow 400 in FIG. 6 to separate the first pressureroller 42 from the main driving roller 41 before starting laserrecording operation. The solenoid 390 is kept energized for apredetermiend period of time, approximately one second, and then thesolenoid 390 is de-energized to allow the first pressure roller 42 tocontact the main driving roller 41. While the first pressure roller 42is separated from the main driving roller 41, any slack 340 of the film100, which has occurred during the film 100 manual setting, iseliminated by the rotation of the main driving roller 41 and the secondpressure roller 43. The first pressure roller 42 is then brought intocontact with the main driving roller 41 again for the normal laserrecording operation after the slack 340 has been eliminated.

Although the slackened film relief mechanism has been described asapplied to the laser recorder, the slackened film relief mechanism isnot limited thereto in its application. The slackened film reliefmechanism effectively elminates the slack of continuously deliveredaccording medium, which has occurred in the recording medium setting tovarious recording medium advancement systems before starting the variousadvancement systems.

Film Pressing and Separating Mechanism to and from the Heat Roller

Referring to FIGS. 1, 2, 7 and 8, a laser recorder, including amachanism for pressing and separating the film to and from the heatroller, according to the present invention, is explained.

The heat-development unit 6 comprises a heat roller 60, a deliverydriving roller unit 61, a guide roller unit 62 and a swing roller 63a.The heat roller 60 has an outer circumference 6a onto which the film 100is brought into contact and by which the film 100 is heated. Thedelivery driving roller unit 61 and the guide roller unit 62 aredisposed on opposite sides of the heat roller 60 to guide the film 100.The swing roller 63a is disposed between the delivery driving rollerunit 61 and the guide roller unit 62 and functions to contact andrelease the film 100 from the heat roller 60 by applying force to one ofthe film surfaces.

The delivery driving roller unit 61 comprises a smaller diameter drivingroller 611, which interlocks with a DC motor, and a large diameterdriven roller 612, which presses the film 100 against the driving roller611 and is driven by the driving roller 611 through the film 100.

The guide roller unit 62 comprises a smaller diameter driving roller621, which interlocks with a DC motor, and a larger diameter drivenroller 622, which presses the film 100 against the driving roller 621and is driven by the driving roller 621 through the film 100.

The swing roller 63a is disposed at the same side of the film 100 as theheat roller 60. The swing roller 63a swings and urges the film 100 torelease it from the heat roller 60.

A solenoid (not shown) may be used as an actuator for swinging the swingroller 63a. When the solenoid is energized, the solenoid magneticallyattracts and keeps the swing roller 63a at a position away from thebackside of the film 100. When the solenoid is de-energized, thesolenoid is swung to contact the film 100 and urge the film away fromthe heat roller 60 with pressure.

The film 100 is set in advance so that its backside contacts the heatroller 60 during heat-development while the film 100 is stretched bytensile force between the delivery driving roller unit 61 and the guideroller unit 62.

During heat-development, the swing roller 63a, disposed at the same sideof the film 100 as the heat roller 60, is placed at a position away fromthe film 100 so that it does not apply a force to the backside of thefilm 100. Thus, the film 100 maintains the stretched state by thetensile force effected between the delivery driving roller unit 61 andthe guide roller unit 62, which are disposed at both sides of the heatroller 60.

During the contact with the heat roller 60 between the delivery drivingroller unit 61 and the guide roller unit 62, a certain amount of heat,which is necessary for heat-development, is given to the film 100 by theheat roller 60. Thus, image information, recorded on the film 100 by theimage recording unit 5, can be heat-developed.

An image density detector of the heat-developed image information on thefilm 100 is diposed between the heat-development unit 6 and theheat-developed film take-up unit 3 on the film path 10. The imagedensity detector comprises a light emitting diode 91 and a photodiode 92which are disposed facing the front and backside of the film 100,respectively.

In the laser recorder comprising the film pressing and separatingmechanism to and from the heat roller as constructed above, the film 100is driven and advanced at a fixed speed by the main driving unit 4, andthe emulsion-coating front surface of the film 100 is exposed to thelaser beam radiation from the image information recording unit 5 whileits backside surface is brought into contact with the outercircumference of the main driving roller 41. After the laser beamradiation, the film 100 is advanced while being guided by the deliverydriving roller unit 61 and the guide roller unit 62, and the backside ofthe film 100 is brought into contact with the heat roller 60 between thedelivery driving roller unit 61 and the guide roller unit 62 toheat-develop the emulsion-coated front surface of the film 100. Then,the film 100 passes through the image density detector 9 and is taken upby the film take-up reel 31.

When the film advancement or the heat-development is stopped, the swingroller 63a swings from a position specified by the continuous line inFIG. 7, or from a position specified by the broken line in FIG. 8, to aposition specified by the continuous line in FIG. 8, and urges the film100 to release it from the heat roller 60. Thus, a high-temperature heatfrom the heat roller 60 is not transmitted to the film 100 because thefilm 100 does not contact the heat roller 60 when the film 100advancement is stopped. Accordingly, the film 100 is free from adverseeffects of the high-temperature heat because the film 100 does notreceive the high-temperature heat at one portion thereof for long timewhen the film advancement is stopped. The film 100 can be heat-developedagain as described above when the swing roller 63a is brought back tothe position specified by the broken line from the position specified bythe continuous line in FIG. 8 and the film 100 is advanced whilecontacting the heat roller 60.

Referring now to FIGS. 9 and 10, a laser recorder, comprising a firstalternative embodiment for the film pressing and separating mechanismfrom the heat roller, according to the present invention, is explained.The same configurations and operations as the first preferred embodimentare not explained.

In the case of this first alternative mechanism, the swing roller 63b isdisposed at the side of the film 100 opposite to the heat roller 60. Theswing roller 63b swings to urge the film 100 into contact with the heatroller 60. The film 100 is so set in advance that the backside of thefilm 100 does not contact the heat roller 60 by hanging the filmslackened between the delivery driving roller unit 61 and the guideroller unit 62 when the heat-development is not required.

When image information, recorded on the film 100 by the imageinformation recording unit 5, is required to be heat-developed, theswing roller 63b swings to a position specified by the continuous linein FIG. 10. The film 100 is advanced while contacting the heat roller60. A high-temperature heat of the heat roller 60 is transmitted to thebackside of the film 100, and the image information, recorded on theemulsion-coated surface of the film 100 by the image informationrecording unit 5, can be heat-developed.

When the advancement of the film 100 and the operation of the heatroller 60 should be deactivated to stop heat-development, the swingroller 63b swings back to a position specified by the broken line inFIG. 10, or to a position specified by the continuous line in FIG. 9,from the position specified by the continuous line in FIG. 10, and stopsurging the film 100 toward the heat roller 60. Thereby, the film 100 isreleased from the heat roller 60, and is moved to such a position thatthe film 100 does not receive adverse effects of heat from the heatroller 60. Therefore, the film 100 is not adversely affected by ahigh-temperature heat.

In reference to FIGS. 11 and 12, a second alternative embodiment for thefilm pressing and separating mechanism to and from the heat roller isexplained.

This second alternative mechanism uses one set of the swing roller 63b,disposed at the side of the film 100 opposite to the heat roller 60, anda guide 631, disposed at the side of the film 100 opposite the swingroller 63b. The swing roller 63b and the guide 631 swing in the samedirection. Space is provided between the swing roller 63b and the guide631 so that the film movement cannot be disturbed in the filmadvancement direction. Thus, the swing roller 63b and the guide 631securely guide the film 100 either in the direction to urge the film 100to contact the heat roller 60, or in the direction to release the film100 from the heat roller 60, when the swing roller 63b swings either inthe direction to urge the film 100 toward the heat roller 60, or in thedirection to release the film 100 from the heat roller 60.

The laser recorder, comprising a third alternative embodiment for thefilm pressing and separating mechanism to and from the heat roller,according to the present invention, is illustrated in FIG. 13.

The third alternative mechanism comprises a delivery driving roller unit61 and a guide roller unit 62, respectively disposed before and afterthe heat-development unit 6, which comprises a heat roller 60 withrespect to the film 100 advancement direction, and a swing roller 63a,which is disposed after the delivery driving roller unit 61 and beforethe heat roller 60 with respect to the film 100 advancement direction.The swing roller 63a moves the film 100 up and down perpendicularly tothe film 100 advancement direction, so that an angle formed between thefilm 100 and the heat roller 60 becomes variable.

The third alternative mechanism thus constituted operates as follows.

The film 100 is manually set as illustrated in FIG. 13 before theoperation. A slackened state of the film 100, shown by the broken linein FIG. 13, is liable to occur around the heat roller 60.

When an image information recording unit 5 is turned on, a laser beam isradiated onto the film 100 contacting a main driving roller 41, and dataprinting is started. At the same time, the delivery driving roller unit61 and the guide roller unit 62 start delivering the film 100.

If the above said slackened state of film 100 has not been eliminatedbeforehand, it can be eliminated before the film 100, on which the firstprinting data is written at the main driving roller 41, reaches the heatroller 60 because the speed of the delivery driving roller unit 61 isset slower than that of the guide roller unit 62 by approximately 10%.Namely, the film 100 with the first printing data written is deliveredwhile being pressed against the heat roller 60. After the film 100 withthe first printing data is brought into contact with the heat roller 60by this mechanism, the film 100 is slid over and delivered out of thedelivery driving roller unit 61 under a constant load, because thedelivery driving roller unit 61 is equipped with a friction clutch. Inother words, the film 100 is not only pressed against the heat roller 60but also delivered with a constant tension applied.

As described above, the swing roller 63a is disposed after the deliverydriving roller unit 61 and before the heat roller 60 with respect to thefilm 100 advancement direction. An angle formed between the film 100 andthe heat roller 60 can be varied by moving the film 100 up and downperpendicularly to the film 100 advancement direction with the swingroller 63a. Accordingly, even if the film 100 is delivered at a fixedspeed, development time can be varied freely, because the film 100contacting area with the heat roller 60 can be varied.

Thus, an optimum angle formed between the film 100 and the heat roller60 can be selected while checking the developed film 100, because thefilm 100 contacting time with the heat roller 60 is varied by swingingthe swing roller 63a.

For an altervative to this third alternative mechanism, the swing roller63a may be disposed between the heat roller 60 and the guide roller unit62, disposed after the heat roller 60 with respect to the film 100advancement direction.

Heat Roller Surface Temperature Detector and Controller

Another feature of the laser recorder is that it comprises a surfacetemperature detector, provided to the heat-development unit having theheat roller 60, and a memory for storing temperature data from thesurface temperature detector. For the above surface temperaturedetector, a thermoresistor (thermistor) 60a, which is in slidablecontact with the heat roller 60, is employed as illustrated in FIG. 13.It is desired that the heater 60b be built-in the heat roller 60.

The heater control unit controls heater control currents in accordancewith resistance value variations of the thermoresistor 60a. The heatercontrol unit comprises a circuit as illustrated in FIG. 14. A CPU 201 isone of the main components of the above heater control unit. A heatertemperature detecting circuit 203 and a heater current supply circuitare included in the heater control unit.

The heater temperature detecting circuit 203 converts thermoresistorresistance values that vary in accordance with the thermoresistortemperature variations into electric signals, and inputs the signals tothe CPU 201. An amplifier 200 inputs to an A/D converter 190; analogvoltage signals corresponding to the resistance values of thethermoresistor 60a, which is connected to a reference power supply 210.The A/D converter 190, in turn, converts the analog signals into digitalsignals, and inputs the digital signals to the CPU 201. The CPU 201outputs a driving signal to a triac driver 230 throught an output port220. The triac driver 230 turns on and off a triac 240 (duty control),and controls currents to be supplied to the heater 60b, which isconnected to an AC 100 V power supply through the triac 240. The CPU 201is connected to a RAM 202 (random access memory) and to a ROM 205 (readonly memory) by a bus line. A CPU 201 control program, etc. are storedin the ROM 205. Data shifted from the ROM 205 and the detectedtemperature data are written in and read from the RAM 202 when required.

The surface temperature control operation by the CPU 201, according tothe present invention, is described below with reference to FIG. 15.

The surface temperature of the heat roller 60 is sampled, for instance,every 1.28 sec., and mean temperatures for the 1.28 sec.-period arestored sequentially in the RAM 202. Here, the mean temperatures for the1.28 sec.-period are calculated by the CPU 201 based on the heater 60btemperatures detected at certain internals. When 10 seconds have passed,a sum of estimated temperature variations for the preceeding 10 secondsis divided by the number of the sampled estimated temperaturevariations. Thus, a compensation data taking the heat roller 60 surfacetemperature variation trends is detected. Namely, the current to besupplied to the heater 60b is controlled not only by referencing to thecurrent temperature of heater 60b but also by referencing to the surfacetemperature variation trends.

Thus, a length of pulse signal, namely a pulse width in a predeterminedcycle, to be sent to the triac driver 230 is determined according to theobtained temperature compensation data. Before starting the next stage,the current mean temperature data is stored in the RAM 202, and theoldest mean temperature data in the RAM 202 is discarded.

The foregoing procedure is explained with reference to the followingExpressions (1) and (2):

    YoTAL;=YoTAL+((ACTMP-oLDTMP)×7-RQTMP)tm (1)

    YoCNT;=YoCNT+1                                             (2)

where;

ACTMP: current mean temperature data

oLDTMP: mean temperature data at 10 sec. before

RQTMP: required temperature data (desired temperature e.g., 115° C.)

YoTAL: sum of estimated temperature variations

YoCNT: number of YoTAL data (initial value=0)

HoSEI: compensation value (initial value=128)

oNoFD: pulse width in one cycle (initial value=30)

In Period I shown in FIG. 15, calculations using Expressions (1) and (2)are repeated. The number of calculations repeated depends on thecondition of the case.

At the moment II, the mean estimate temperature variation in Period I iscalculated by using the following Expression (3), where A designates amean estimated temperature variation:

    A=YoTAL/YoCNT                                              (3)

Also at the moment II, either of the following further compensations isdone to a compensation value, HoSEI, determined according to the currentheater 60b temperature depending on the sign of YoTAL values.

(a) YoTAL>0 (Temperature will rise beyond 115° C.):

In case, A<3.7 (°C.), the HoSEI value is further compensated by usingthe following Expression (4):

    HoSEI;=HoSEI-1                                             (4)

In case, A≧3.7 (°C.), the HoSEI value is further compensated by usingthe following Expression (5):

    HoSEI;=HoSEI-2                                             (5)

If this HoSEI; value is less than zero, the lower limit value iscosidered to be zero (0).

(b) YoTAL<b 0 (Temperature will drop below 115° C.):

In case, |A|<3.7 (°C.), the HoSEI value is further compensated by usingthe following Expression (6):

    HoSEI;=HoSEI+1                                             (6)

In case, |A|≧3.7 (°C.), the HoSEI value is further compensated by usingthe following Expression (7):

    HoSEI;=HoSEI+2                                             (7)

If this HoSEI; value is greater than two-hunderd and twenty-five (255),thr upper value is considered to be two-hundred and twenty-five (255).

And then, the oNoFD value, calculated by the following expression (8),determines the pulse width in one cycle for the duty control:

    oNoFD=30+((HoSEI-128)/4)                                   (8)

Namely, the triac 240 is turned on for a period corresponding to thepulse width in the cycle to control the current to be supplied to theheater 60b. Here, the difference, (HoSEI-128), is divided by a quarter(1/4) to avoid a sudden surface temperature variation. (See FIG. 16.)

In FIG. 16, T and τ are specified by the following Expressions (9) and(10):

T=1.28 (sec.) (9)

τ=NoOFD×0.01 (sec.) (10)

Then, the above operations are repeated to adjust the actual surfacetemperature to the required temperature.

Stepping Motor Driving Current Control Circuit

The image information recording unit 5 comprises a laser for recordingand a scanning system for scanning the laser beam in the film widthdirection. One line of image information is recorded in the film widthdirection by a predetermined cycle. The scanning in the filmlongitudinal direction is performed by rotating the main driving roller41 at a low speed. A stepping motor (not shown) for directly driving themain driving roller 41 has an advantage that it can be rotated at a lowspeed according to input pulses. However, stepping motors have a problemthat their angular velocity varies for every one step period, namely,stepping motors have jitter components. Referring to FIGS. 3 and 5, amethod to reduce the jitter components and a control circuit for thispurpose are explained.

The pulse currents of CH1, CH2, CH3 and CH4 having the saw toothwaveform specified in FIG. 3 are supplied to the the stepping motor fordirectly driving the main driving roller 41. The CH1 pulse currentsupplied to the first stator coil terminal gradually increases in thefirst step period, t1. The maximum value of CH1 is maintained for theentire second period, t2. The CH1 current gradually decreases in thethird period. The minimum value of CH1 is maintained in the fourthperiod. The CH2 pulse current supplied to the second stator coilterminal has a different phase from the CH1 pulse current by 180 deg.The CH3 pulse current supplied to the third stator terminal has adifferent phase delayed by 90 deg. from the CH1 pulse current The CH4pulse current supplied to the fourth stator terminal has different phaseadvanced by 90 deg. from the CH1 pulse current. Accordingly, it can beunderstood that the driving current for the stepping motor according tothe present invention varies smoothly, and that the driving current hasjitter components in a smaller degree. In the stepping motor accordingto the present invention, the pulse current of saw tooth waveform, beingdifferent from the conventional rectangular waveform, is applied to thestator terminals to reduce the jitter components.

In the laser recorder according to the present invention, one of thefeatures is to rotate the main driving roller 41 smoothly by controllingthe control current for the stepping motor directly connected to themain driving roller 41 with a stepping motor driving circuit illustratedin FIG. 5. The driving circuit controls the control current so as togradually increase or decrease the control current by one micro stepresulting from the further division of one step angle. As earlierexplained, FIG. 3 illustrates the stepping motor driving currentaccording to the present invention, and FIG. 4 illustrates theconventional stepping motor driving current waveform. The drivingcircuit illustrated in FIG. 5 has a central processing unit (hereinafterabbreviated to "CPU"), a Read only memory connected to the CPU via a busline (hereinafter abbreviated to "ROM"), four D/A converters receivingdata from the CPU via the bus line, and four power amplifiers forgenerating pulse currents of CH1, CH2, CH3, and CH4 in accordance withoutput signals from the D/A converters.

Referring to FIG. 5, the operation of the driving circuit is explainedbriefly.

First, the CPU periodically accesses the ROM to receive recordedelectric current value data, and outputs the electric current data tothe D/A's by a predetermined timing.

Second, the D/A's convert the electric current data to analog voltages,and send the analog voltages to the power amplifiers. The poweramplifiers supply the output electric currents corresponding to theanalog voltages to the stator coil terminals (not shown) of the steppingmotor. The power amplifier for channel 1 comprises an amplifier 160, anoutput current detecting circuit 180, and an output amplifier 170. Thechannels 1 through 4 to be connected to the stepping motor are connectedto the primary amplifier 160 via the D/A converter. The primaryamplifier 160 converts the voltage into the currents. The secondaryoutput amplifier 170, connected to the stepping motor, further dividesone step angle of the control current by micro steps, and sends thecontrol current by increasing or decreasing micro steps. The outputcurrent detecting circuit 180, inversely connected to the secondaryoutput amplifier 170, is a differential amplifier. The output currentdetecting circuit 180 feeds back phase signals to the secondaryamplifier 170, and controls the secondary amplifier 170 so as togenerate output currents corresponding to the analog voltage values ofthe D/A converter. The input data to the D/A converters are sequentiallyread out of a table in the ROM. The data to be written in the ROM isobtained by measuring jitter components of stepping motors to be used inthe laser recorder. Thus, optimum current data for reducing the jittercomponents are written in the ROM. As for the channels 2 through 4, thesame configurations as described above are employed in channels 1through 4.

The output driving circuit control operation is explained in detail. Thestep periods, t1, t2, t3, and t4 are each divided into 1024 micro stepperiods. Because 0.9 deg. of stepping motor rotation angle correspondsto one step period, the stepping motor rotates once when 400 stepperiods have passed.

When a main driving roller having a 30 mm diameter is used, the one steplength, L, is calculated by the following expression:

    L=30×(0.9/360)=0.2356 (mm)

The film advancement speed is 2.5 mm/sec. and the step periods, t1, t2,t3 and t4 are divided into 1024 micro step periods. Therefore the timerequired for one step, t, and the time required for one micro step, msp,are calculated by using the following expressions respectively:

t=0.2536/2.5=94.25 (millisecond/step)

msp=94.25/1024=92.039 (microsecond/micro step )

Therefore, the first step period t1 is divided into msp1 throughmsp1024, and the second step period t2 is divided into msp1025 throughmsp2048, and the third step period t3 is divided into map2049 throughmsp3072, and the fourth step period t4 is divided into msp3073 throughmsp4096.

Accordingly, when output current values for the 4096 micro steps of thefirst channel current, CH1, are stored in the ROM, it is necessary onlyto store currents having different phases for the second, third, andfourth channel currents, namely CH2, CH3, and CH4. Specificallyspeaking, the CPU divides the input clock signals equally on thecircumference to generate the micro step pulse signal corresponding tothe micro step period.

The CPU has a built-in 12-bit counter (not shown) for counting the microstep pulse signals. The counter outputs 2-bit micro step displayinformation to specify the micro step periods. Because the D/Aconverters are 12-bit D/A converters, the ROM having 48-Kbit or morememory capacity stores 12-bit current values for every micro stepperiod. And the CPU composes a memory address of the ROM storing thecurrent value for the next "m+1"th micro step period in accordance withmicro step display information displaying the "m"th micro step period.Then, the CPU accesses the ROM memory address to receive the channelcurrent, A1, for the "m+1"th micro step period from the ROM andpreserves the channel current, A1, for the "m+1"th micro step period.Similarly, the CPU composes a memory address of the ROM storing thecurrent value for "m+1025"th micro step period, and accesses the ROMmemory address to receive the channel current, A4, for the "m+1025"thmicro step period from the ROM and preserves the channel current, A4,for the "m+1025"th micro step period. In accordance with the samemethod, the CPU composes memory addresses for the ROM storing thecurrent values for "m+2049"th and "m+3073" micro step periods, andaccesses the ROM memory addresses to receive the channel current, A2,for the "m+2049"th micro step period and the channel current A3 for the"m+3073" micro step period from the ROM and preserves the channelcurrent, A4, for the "m+1025"th micro step period. During the "m+1"thmicro step period, the CPU continues to output the current values of A1,A2, A3, and A4 to the D/A converters, and then, the CPU reads currentvalues for the "m+2"th, the "m+1026"th, the "m+2050"th, and the"m+3074"th micro step periods out of the ROM. Because the current valuesA1 and A3, and the current values A2 and A4, are in a complementaryrelationship, the A2 and A4 current values can be generated by receivingA1 and A3 current values from the ROM and finding their complementvalues. Because the number of micro step periods are so set that it willbe one dot width of the main driving roller 41 or less, the variation ofone micro step width is reduced. Thus, favorable quality printing, inwhich printed dots are distinctly identified by controlling torques, isgenerated during the micro step periods.

For the stepping motor controller according to the present invention, itis possible to construct the following modified embodiments:

(1) For the stepping motor, various types of motors other than thosedescribed above may be employed.

(2) It is possible to reduce the jitter components by controlling pulsevoltages to be applied to the stator coil terminals instead of bycontrolling the currents to be supplied to the stator coil terminals.

(3) The voltage waveforms to be applied to the stator coil terminals orthe current waveforms to be supplied to the stator coil terminals arenot limited to the saw tooth waveform illustrated in FIG. 3 but they canbe determined as desired depending on loads applied to stepping motorsand the characteristics of stepping motors.

(4) The waveforms to be applied to the stator coil terminals or thecurrent waveformms to be supplied to the stator coil terminals do notnecessarily have similar waveforms for the channels 1 through 4.

Film Storing Mechanism

A film storing mechanism according to the present invention isillustrated in FIG. 17. The film storing mechanism comprises a cutter 33for cutting the film 100 to a predetermined length, and a tray 32 forstoring the film 100 delivered out of the cutter 33, and a pressureroller 250 and a delivery roller 260 for delivering the film 100 to thetray 32.

In the film storing mechanism, after the film 100 is cut by the cutter33, the delivery roller 260 is separated from the pressure roller 250for a predetermined time to stop the film delivery and to overlap theleading edge of the film 100, which is to be cut in the next cutting, onthe trailing edge of the film 100, which has been already cut, in apredetermined length.

The film storing mechanism thus constituted operates as follows.

In the cutting operation mode, a cut mark is marked at a predeterminedposition on the film 100. The cut mark is detected by a sensor (notshown), disposed near the cutter 33. And the sensor provides a signalfor stopping the film 100 delivery by separating the delivery roller 260from the pressure roller 250, and for actuating the cutter 33 after apredetermined time has passed.

Upon the detection of the cut mark on the film delivered out of the heatroller 60, the sensor provides the signal to the cutter 33, and thecutter 33 waits for a predetermined time measured by a timer, and cutsthe film 100 at a predetermined position to a predetermined length. Thecut film 100 has been advanced along the guide plate 280, and theleading edge of cut film 100 has already been nipped between thedelivery roller 260 and the pressure roller 250.

When a lever 290, equipped with the delivery roller 260, is urged by asolenoid 300 to separate the delivery roller 260 from the pressureroller 250, the delivery roller 260 is swung counterclockwise around theshaft 310. As the delivery roller 260 is separated from the pressureroller 250 for a certain period of time, the film 100 delivery isinterrupted. On the other hand, the film 100 to be cut in the nextcutting is delivered at a fixed speed, and the leading edge of the film100 to be cut overlaps on the trailing edge of the cut film 100. Theoverlap is designated by 210 in FIG. 17. The width of overlap 210depends on the period of time for which the delivery roller 260 isseparated from the pressure roller 250. After a predetermined time haspassed, the solenoid 300 is de-energized to bring the delivery roller260 back into contact with the pressure roller 250 to restart the film100 delivery. Accordingly, the cut film 100 and the film 100 to be cutin the next cutting are delivered to the tray 32 while holding theoverlap, the cut films 100 are guided by a retaining spring 320 andstored in the tray 32.

Accordingly, the cut films 100 are delivered out of the delivery roller260 and the pressure roller 250, and stored in the tray 32 sequentiallyin the correct order when the film 100 is continuously delivered. Incase of a take-up operation mode, the film 100 is not cut by the cutter33, therefore, it is possible to take-up and store the film 100continuously in a reel without separating the delivery roller 260 fromthe pressure roller 250.

What is claimed is:
 1. A laser recorder, comprising:film feed means forfeeding a film in a roll; film take-up means for taking up the film;driving means for driving the film at a fixed speed, disposed on a filmpath extending between said film feed means and said film take-up means;and image information recording means for radiating a laser beam in awidth direction of the film that is driven by said driving means,comprising a laser optical system; said driving means comprises: a maindriving roller which has an outer circumference to be in contact withthe film and is driven in a predetermined direction by a stepping motorat the fixed speed; a first pressure roller that is pressed against theouter circumference at a first position to nip the film therebetween andis driven by the main driving roller; a second pressure roller that ispressed against the outer circumference at a second position and isdriven by the main driving roller, said second position being downstreamof the first position in the driven direction of said main drivingroller, the film being exposed by the laser beam radiated through aposition between said first and second pressure rollers; a feed drivingroller that feeds the film to said main driving roller with forming aloop of the film; and a delivery driving roller that delivers the filmfrom said driving roller with forming a loop of the film; therebyapplying no force of feeding and delivering the film to and from saidmain driving roller.
 2. A laser recorder according to claim 1, whereinfilm loop detectors are provided between said feed driving roller andsaid main driving roller, and between said main driving roller and saiddelivering driving roller, respectively, andsaid feed driving roller andsaid delivery driving roller are controlled in accordance with signalsgenerated by said film loop detectors.
 3. A laser recorder, comprising:afilm feed unit; a film take-up unit; a main driving roller for driving afilm drawn out from said film feed unit continuously; a stepping motorfor rotating said main driving roller in a predetermined direction; afirst pressure roller that is pressed against the outer circumference ofsaid main driving roller at a first position to nip the filmtherebetween and is driven by said main driving roller; a secondpressure roller that is pressed against the outer circumference of saidmain driving roller at a second position to nip the film therebetweenand is driven by said main driving roller, said second position beingdownstream of said first position in the rotating direction of said maindriving roller; image information recording means for radiating a laserbeam in a width direction of the film through a position between saidfirst and second pressure rollers; film loop forming means each forforming a loop of the film before and after said main driving rollerwith respect to a direction of film advancement; and control means forcontrolling an amount of the loop formed by each film loop forming meanswithin a desired amount.
 4. A laser recorder according to claim 3,wherein the amount of film loop before said main driving roller withrespect to the direction of film advancement is kept within apredetermined range by controlling a film drawn-out amount out of saidfilm feed unit.
 5. A laser recorder according to claim 3, whereinaheat-development unit is provided upstream of said film take-up unitwith respect to the film advancement direction, and the amount of filmloop after said main driving roller with respect to the direction offilm advancement is kept within a predetermined range by controlling afilm advancement speed toward said heat-development unit.
 6. A laserrecorder, comprising:film feed means for feeding a heat development filmstored in a role; a heat developed film take-up unit; main driving meansfor driving the film at a fixed speed, disposed on a film path extendingbetween said film feed means and said film take-up unit; imageinformation recording means for radiating a laser beam in a widthdirection of the film which is driven by said main driving means,comprising a laser optical system; heat development means forheat-developing an image information recorded on the film by said imageinformation recording means, disposed between said main driving meansand said heat-developed film take-up unit on the film path; wherein saidheat development means comprises: a heat roller having an outercircumference with which the film is brought into contact and by whichthe film is heated; and a swing roller for selectively urging one sideof the film from a first position wherein the film is separated fromsaid heat roller to a second position wherein the film is in contactwith said heat roller.
 7. A laser recorder according to claim 6, whereinsaid swing roller is disposed at the same side of said heat roller andswings to urge the film to the other side to separate the film from saidheat roller.
 8. A laser recorder according to claim 6, wherein saidswing roller is disposed at an opposite side to the side of the heatroller against the film, and swings to urge the film to be brought intocontact with said heat roller.
 9. A laesr recorder, comprising:a filmfeed unit; a film take-up unit; main driving means for driving a filmdrawn out of said film feed unit; image information recording means forradiating a laser beam in a width direction of the film which is drivenby said main driving means; heat development means for heat-developingan image information recorded on the film; means for detecting a surfacetemperature of said heat development means; means for storingtemperature data given from said surface temperature detector; and meansfor controlling a current to be supplied to said heat development meanson a basis of the stored temperature data and the present temperaturedata.
 10. The laser recorder according to claim 9, wherein said heatdevelopment means comprises a heat roller having a built-in heater andsaid detecting means includes a thermoresistor.
 11. A laser recorder,comprising:a film feed unit; driving means for driving a film drawn outof said film feed unit; an image information recording means forradiating a laser beam in a width direction of the film that is drivenby said main driving means; a cutter for cutting an image informationrecorded film to a desired length; a tray for storing the film deliveredout of said cutter; delivery means for delivering the cut film to saidtray; and means for releasing the operation of said delivery means for apredetermined time to stop a film delivery after cutting by said cutter,wherein a leading edge of a film to be cut in a next cutting isoverlapped in a predetermined length on a trailing edge of the film thathas been cut